1. Field of the Invention
The instant invention is directed to an improved collimation lens device for use in multiple communication channel array of optical fiber lines having a gap in the array. A component of the device also has utility with a single fiber line having a gap in the line.
2. Description of the Prior Art
The device of the present invention especially satisfies a requirement arising in connection with optical fiber rotary joints for interposition in multiple communication channel arrays of optical fiber lines. Multiple channel rotary joints for multi-mode fibers have been developed but the resultant optical trains exhibit high optical loss and the channels exhibit undesired crosstalk. Additionally, the extreme tolerances associated with single-mode fibers preclude the easy adaptation of rotary joints to handle single-mode fiber. The tight tolerances required by single-mode fibers generally result in excessive loss. Rotary joints for single-mode fiber have been developed, but are limited to a single on-axis fiber.
Illustrative of the prior art is U.S. Pat. No. 4,872,737 to T. Fukanori et al, in which precision beam registry across a gap between an array of in optical fibers is obtained by lenses that perform collimation at each side of the gap which further interposition of reflectors to optically guide the individual collimated channel beams with a shortened beam path distances between collimating lenses. This arrangement tends to be complex expensive, and to require a sizeable transverse dimension of required envelope space for a given array of optical fibers. It is to be appreciated that an important motivation for the use of complex organization of this development is the fast degradation of energy coupling across the gap as a function of gap distance in rotary joints for arrays of fiber optic lines.
Typically in the heretofore known rotary joints for multi-mode fibers, ferrule reinforce terminal end sections of fibers were simply mechanically inserted into lens holders for gradient index glass, rod-type miniature collimation lenses with of fiber simply concentrically aligned with its associated rod-type collimation lens.
As mentioned, satisfactory lensing arrangements for rotary joints for single-mode fiber are, prior to the present invention, non-existent.